I do a little pitching with my friend and just started trying some breaking balls like a slider or curveball 12-6.the thing is when i manage to actually curve the ball it curved right before his glove so he missed catching it .But if there was a batter in front of him it would still be a fastball to the batter only a step after it finally broke down.So is there a way to know when the ball will curve?

A release point that is further out front will generally produce better movement as it is a stronger position from which to spin the ball. So perform your mechanics well - proper sequencing and good timing - and that should result in the release point out front and the movement you want (assuming proper technique).

Keep in mind that late movement is generally a good thing so don’t try to move up the breaking point too much.

I agree with what everyone else has said. If you get a release point out in front of your body, it will increase spin rate and give better movement.
Be aware the release point is a function of the shape of your pitch. Pay catch at full speed throwing the curve to learn the shape, then once you get it down you can learn to control it by refining release points.
Timing can certainly be tough, but I think it’s the last thing to worry about. Learn to throw it hard and timing won’t be an issue. Timing seems to be an issue when learning if not throwing it hard. If you throw it hard, your body takes care of the timing. If you throw it softy, your timing will be shot.

Also try checking as many curveball grips as you find… some pitchers just don’t get that exact Koufax-Ryan-Kershaw curveball, you might just get sweeping, or ‘‘slurving’’ actions.
I’d say you just try and check when playing catch, also it’s an offspeed, it should look like a fastball (arm-action wise) but you don’t really need to throw it 80+, just focus on controlling the break and pin-pointing it.
Greetings from Cartagena